The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Many automotive body panels are mass produced from wrought sheet metal, typically wrought steel alloys using a stamping process carried out by a stamping press. During the stamping process, a work piece is formed to a desired shape and cut to produce a sheet metal part. More specifically, forming dies are brought into contact with the work piece to deform the work piece into the desired shape and cutting dies shear the work piece.
Some automotive body panels are mass produced from cast metal using a casting process carried out by a casting machine. Typically, the metal is an alloy of aluminum or magnesium, and the casting process is a high-pressure die casting process. During the casting process, molten metal is poured into a mold defining a semi-finished shape of the panel and allowed to cool to solidify. The solidified part is then removed from the mold and trimmed and/or pierced using one or more presses and hardened tools. In automotive bodies, cast panels conventionally are used as inner panels, rather than exterior panels, on door assemblies and lift gates.
However, some steel alloys and cast magnesium alloys used to make the automotive body panels have low corrosion resistance and corrode when exposed to moisture and various substances found in the environment, such as salt used to melt snow and ice on the roads. Accordingly, sheet metal parts used to create the panels may be coated with a thin layer of zinc by the steel supplier using a galvanizing process. After undergoing the forming process, the panels are typically cleaned and coated with a surface treatment including, for example, phosphate, electro-deposited epoxy, and paint. The surface treatment provides a barrier of corrosion-resistant material between the damaging environment and the sheet metal part.